Follow the ridge trail to reach the source of the Guil after crossing several small streams. Wade across the Guil (2,450m) and after a few bends in the trail, you will arrive at the Lestio lake (2,510m). Take a winding, uphill trail and then in a south-easterly direction, walk below the crest of Pointe Joanne and continue to the Valante pass (2,815m), which is a border pass.
(Marc Buisson, CDRP 05)

Between green shale and rosy gneiss, this cross-border stage penetrates the mythical mineral world of the Viso mountain, the highest sentinel of the Southern Alps (3,841m). To the South of the Viso Hut, a vast and modern structure renovated in 2003, the trail heads over alpine pastureland on which wolves and flocks of sheep live alongside each other as best they can. The stock routes mark out these grassy stretches irrigated naturally on all sides. The central stream here comes from the Lestio lake and later widens out to become the Guil river.
The climb to the Valante pass, a passage between the Queyras Regional park and the Italian Piedmont, crosses a hillock of darn shale and almost permanent firns. The pass is an unmissable observation point for ibexes (reintroduced to the Queyras region between 1995 and 1998) that came to scrape the lichen from the rocks there. This spot is sometimes covered in nebia, a thick and humid mist in Italian. The carpets of Koch’s and royal blue gentians and the golden yellow arnica flowers are then masked.
The Piedmont valleys stretch out to the South, and the rock turns from green on the French side to pink in Italy.
The stone pyramid of mythical size and shape of Mount Viso is a vestige of the emergence of the Alps. The marls and sediment accumulated here when it was still part of the ocean were thrust upwards at the time of the collision of the two tectonic plates on either side of the “alpine rift” (a submarine fissure caused by the sliding of the plates). They form the medium-altitude summits of the region, as they have already to a large extent been planed down by erosion. However, deep magmas also escaped from this rift, and as they are more resistant, it is they who offer mountaineers the most vertiginous summits of the massif, including the most emblematic Mount Viso. Currently, the rock visible there is composed of ophiolitic complex, typical lava from these old rifts, green basalt-based rock (volcanic rock) and gabbro, from gneiss (metamorphic rock) and sediment. These geomorphological particularities make it a prized subject of analyses and its impressive shape generates numerous myths and legends.
(Sara Zeidler, Gilles Chappaz, Grande Traversée des Alpes)